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United States Patent |
5,271,732
|
Yokokawa
|
December 21, 1993
|
Heat-treating apparatus
Abstract
A heat-treating apparatus comprises a heat portion which performs a
required heat treating to a plural number of objects to be treated mounted
on a heat-treating boat, a vacuum exhaust system which creates a vacuum
inside the heat-treating portion, a load lock chamber which is connected
so as to be freely openable and closable with respect to the heat-treating
portion, which is filled therein with an inert gas and which is for
transporting an object to be treated into and out of the heat-treating
portion, and a residual treating gas exhaust system which is connected to
the load lock chamber. Furthermore, in this heat-treating apparatus, there
are also provided an oxygen concentration detector for detecting an oxygen
concentration inside the load lock chamber, a door lock device provided in
a vicinity of a maintenance door of the load lock chamber and which
regulates opening and closing of the maintenance door, and a door lock
control device which releases a lock of the door lock device when the
oxygen concentration detector has detected a required oxygen
concentration.
Inventors:
|
Yokokawa; Osamu (Kanagawa, JP)
|
Assignee:
|
Tokyo Electron Sagami Kabushiki Kaisha (Kanagawa, JP)
|
Appl. No.:
|
858002 |
Filed:
|
March 26, 1992 |
Foreign Application Priority Data
| Apr 03, 1991[JP] | 3-98132 |
| Apr 03, 1991[JP] | 3-98133 |
Current U.S. Class: |
432/241; 432/5; 432/6 |
Intern'l Class: |
F27D 003/12 |
Field of Search: |
432/5.6,241,153,151
|
References Cited
U.S. Patent Documents
4943235 | Jul., 1990 | Nakao et al. | 432/6.
|
4955808 | Sep., 1990 | Miyagawa | 432/5.
|
4976613 | Dec., 1990 | Watanabe | 432/241.
|
5055036 | Oct., 1991 | Asano et al. | 432/6.
|
5131842 | Jul., 1992 | Miyazaki et al. | 432/6.
|
Primary Examiner: Yuen; Henry C.
Attorney, Agent or Firm: Beveridge, DeGrandi, Weilacher & Young
Claims
What is claimed is:
1. A heat-treating apparatus comprising:
a heat-treating region for heat treating a plural number of objects to be
treated mounted on a heat-treating boat;
a vacuum exhaust system for creating a vacuum inside said heat-treating
region;
a load lock chamber fillable with an inert gas, for transporting objects to
be treated into and out of said heat-treating region;
an inert gas supply system for supplying an inert gas from an inert gas
supply source to said load lock chamber;
a residual treating gas exhaust system connected to said load lock chamber,
for exhausting residual gas from said load lock chamber;
an opening portion provided at a lower end of said heat-treating region;
and
a manifold connected to said opening portion and said vacuum exhaust
system, said manifold being provided with cooling means to cool said
manifold.
2. The heat-treating apparatus according to claim 1, wherein said objects
to be treated is a semiconductor wafer.
3. The heat-treating apparatus according to claim 1, wherein said cooling
means includes a double-walled structure forming a cooling water path for
cooling water flow therein.
4. The heat-treating apparatus according to claim 1, further including a
treating gas inlet pipe provided at an upper portion side wall of said
manifold for leading a processing gas thereinto.
Description
BACKGROUND TO THE INVENTION
The present invention relates to a heat-treating apparatus provided with an
interlock function for a maintenance door of a load lock chamber, and a
treating gas exhaust duct.
In general, in apparatus such as oxidation dispersal apparatus and other
apparatus for the heat-treating of semiconductor wafers, the oxidation
dispersal reaction is performed in a high temperature status of
1200.degree. C. for example, when compared to film growth processing by
the CVD method. Because of this, when metal materials are used in the
furnace portion of the heat treating furnace, metallic contamination of
the semiconductor wafers may occur and when a corrosive gas is used as the
treating gas, the metallic members that configure the interior of the
furnace are corroded and the products formed are dispersed and attach to
the surface of the semiconductor wafer, so that there is also the danger
of their performance deteriorating. It is because of this that the
treating vessel of a heat-treating furnace is configured of glass or some
substance that has corrosion resistance and heat resistance. A tube for
the introduction of the treating gas to the treating vessel of the
heat-treating furnace and a tube for the exhaust of the gas after
treatment are made of glass, and are mounted to form a unit with the
heat-treating apparatus itself in a configuration where steam or the like
is supplied to inside the treating vessel and oxidation dispersion
treating for the semiconductor wafer is performed at normal pressure and
in a high-temperature status of 200.degree. C. for example.
Recent high integration of LSI such as the improved mounting density of
MOSFET for example, has led to recent LSI such as 1.4M DRAM for example,
having a minimum design width of 1 .mu.m or less, and for the film
thickness of the gate oxide film being 200 .ANG. or less. Also, the gate
oxide films of 16M DRAM are also tending to be thinner than 100-150 .ANG..
When the pre-processing prior to the film formation of the semiconductor
wafer involves wetting and cleaning the silicon surface by HF
(hydrofluoric acid) and HCl (hydrochloric acid), there is a clean silicon
surface on the semiconductor wafer after cleaning but the oxygen and water
components in the atmosphere soon react with the silicon to form a natural
oxidation film about 10 .ANG. thick on the surface.
In addition, when there is a lateral type of heat-treating furnace, the
boats mount the semiconductor wafers mounted to them are driven in the
horizontal direction into a reaction vessel that has been heated to
1000.degree. C. for example and are loaded, and there is the possibility
that an opposing air flow caused by the temperature difference between the
inside and the outside of the furnace may cause air to enter into the
reaction vessel of the heat-treating apparatus. Because of this, when
there is a lateral type of furnace, it is not possible to avoid the heated
wafer reacting with the oxygen in the air when there is loading, and a
natural oxidation film of 50-100 .ANG. thick forming on the surface of the
water. Also, since this natural oxidation film is porous and has a poor
film quality, there is a limit to application to the high density elements
for which control of the gate oxide film is necessary.
On the other hand, when a vertical type of heat-treating furnace is used,
there is little intake of oxygen to inside the reaction vessel when
compared to the case for the horizontal type of furnace and the thickness
of the natural oxidation film formed is small at 30-50 .ANG.. Because of
this, vertical type heat-treating furnaces are mainly used for film growth
in semiconductor wafers for 1M DRAM.
However, with high densities of 4M and 16M for LSI, air is also taken in
when there is loading and unloading to and from the furnaces used, and
this, and the moisture component absorbed by the wafer cause the formation
of a natural oxide film for which improved control is necessary. In
particular, with increasingly high densities for semiconductor elements,
control of the film thickness of the oxide film, control of the generation
of the natural oxide film of around 10 .ANG. and which is formed by the
reaction between silicon and the water and oxygen in the atmosphere during
the time after the wafer has been cleaned and when it is being transported
to the heat-treating furnace, and the exclusion of oxygen and the residual
water component inside the heat-treating furnace and that becomes the
cause of the formation of the natural oxidation film are essential.
In addition, semiconductor wafer processing apparatus other than apparatus
for the formation of oxide films also require control of the generation of
excessive natural oxidation films when there is the formation of
capacitance films and polysilicon films that require particularly small
contact resistances.
The present invention has as an object the effective elimination of these
problems and the provision of a heat-treating apparatus that can control
the formation of natural oxidation films on semiconductor wafers when
there is wafer loading to a heat-treating apparatus.
Also, in general, for vertical type heat-treating apparatus there has been
proposed (such as in "Electronic Materials" (Denshi Zairyo) March, 1989;
pages 38, 39) a load lock method that uses a configuration for the
airtight control of the atmosphere when the semiconductor wafers are
loaded to the furnace.
The conventional load lock method that is disclosed here has a boat raising
and lowering mechanism and the like arranged at the bottom of a vertical
type of heat-treating furnace, arranged inside a load lock chamber, and
after the inside of the chamber has been made a vacuum, an inert gas such
as nitrogen or the like is completely filled into the chamber. The loading
of the boat to inside the furnace is performed after this. As a result,
the natural oxidation of the surface of the wafer is prevented when there
is loading, and the formation of natural oxidation films is strongly
controlled.
In a load lock chamber of a vertical type of heat-treating furnace such as
described above, it is necessary to perform maintenance of the boat
raising and lowering mechanism that is housed inside it, or to clean the
film that has adhered to the wafer boat for example, and so the
maintenance door to the load lock chamber must be opened and closed
comparatively frequently. In this case, the workers must enter the chamber
in order to perform work to take the lowered wafer boat for example, to
outside of the chamber. However, as has been described above, the inside
of the chamber is filled to normal pressure with nitrogen or some inert
gas, and in a worst case, entering the chamber could result in
asphyxiation of the worker.
Not only this, even in cases where a worker stands near the door leading to
the chamber but does not enter the chamber, the worker is nevertheless
enveloped in a large amount of nitrogen gas when the maintenance door is
opened. In addition, the capacity of the chamber is tending to become
larger in order to house wafer boards for which the diameter is increasing
to 8 inches or more, and for which the batch processing number per time is
also increasing. This means that the problem described above must be
solved all the more urgently.
In the light of the problem described above, the present invention is
proposed for the effective elimination of the problem described above, and
has as an object the provision of an interlock mechanism that releases the
lock of the maintenance door of the chamber after the gas filled inside
the load lock has been replaced by air and the oxygen concentration has
attained a required value.
SUMMARY OF THE INVENTION
With the heat-treating apparatus of the present invention, there are
provided a heat-treating portion that performs a required heat-treating to
a plural number of semiconductor wafers or some other object for treating,
a vacuum exhaust system for creating a vacuum inside said heat-treating
portion, and a load lock chamber connected to the heat-treating portion so
as to be freely openable and closable, for the carrying in and out of the
object of treatment to and from a heat-treating portion and for filling an
inert gas into the heat-treating portion.
Furthermore, there are also provided a heat-treating portion that performs
a required heat-treating to a plural number of objects to be treated and
which are housed in a treating boat, a manifold connected to an opening
portion of the heat-treating portion, a vacuum exhaust system connected to
the manifold and for creating a vacuum inside the treating portion, and a
cooling means for cooling the entire manifold.
According to the present invention, the vacuum exhaust system is driven
after the completion of oxidation treatment or some other heat treatment
for the object of treatment inside the heat-treating portion, and the
water vapor and oxygen components that cause the formation of the natural
oxidation film by remaining inside the heat-treating portion are thereby
exhausted. After this, the atmosphere inside is replaced with an inert gas
such as nitrogen and made normal pressure. Then, the treated object of
treatment is unloaded to the load lock chamber that is already held at
normal pressure by the inert gas. When this is done, the heat-treating
portion and the load lock chamber are connected but the steam and oxygen
components inside the heat-treating portion have already been exhausted
and so there is no flowing of these to inside the load lock chamber.
According to another invention of the present application, a vacuum is
created in the status where the objects of treatment have been loaded to
the heat-treating portion, and the steam and oxygen components inside are
exhausted. When heat treating such as oxidation dispersal processing for
example is performed to the object of treatment in the heat-treating
portion, the entire manifold is cooled by a cooling means so that the
surface of the metal manifold does not have its surface corroded by the
metallic contamination of the semiconductor wafers and the gases when
corrosive gases are used because of its high temperature. Then, after the
completion of the heat-treating operation, the supply of treating gas to
the heat-treating is stopped, the vacuum exhaust system connected to the
manifold is driven and the steam, oxygen components and treating gas
remaining inside the load lock chamber are exhausted. After this, the
internal atmosphere is replaced by nitrogen and made normal pressure and
the treated objects are unloaded.
Furthermore, according to still another invention of the present
application, in an interlock apparatus that controls an opening and
closing of a load lock chamber of a heat-treating apparatus that has been
filled with an atmosphere such as nitrogen for example, is provided in the
vicinity of a maintenance door inside the chamber, with an oxygen
concentration detector that detects a concentration of oxygen inside the
chamber, a door lock means that regulates the opening and closing of the
maintenance door, and a door lock control means that releases the lock of
the door lock means then the oxygen concentration detector detects a
required concentration of oxygen.
According to the present invention, the load lock chamber that is filled
with a gas other than oxygen, such as nitrogen for example, normally has
the maintenance door locked by the door lock means to that it either does
not open at all or opens only slightly. Then, when there is to be
maintenance inside the chamber, the nitrogen gas inside the chamber is
exhausted by the supply and exhaust system and is either forcedly
replaced, or the maintenance door is opened slightly and the nitrogen gas
is allowed to be naturally replaced by the outside air. Then, when the
oxygen concentration detector detects a required oxygen concentration in
the chamber, the door lock control means releases the door lock means and
allows the maintenance door to be fully opened.
Other additional objects and features of the present invention will become
clear from the following description, with reference to the appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view of an entire configuration of a heat-treating apparatus of
the present invention;
FIG. 2 is a longitudinal sectional view of a load lock chamber and a
heat-treating portion of a heat-treating apparatus of the present
invention;
FIG. 3 is a partially enlarged sectional view showing major portions of a
heat-treating portion of a heat-treating apparatus of the present
invention;
FIG. 4 is a plan view of a load lock chamber of a heat-treating apparatus
of the present invention;
FIG. 5 is a frontal elevation view of a load lock chamber of a
heat-treating apparatus of the present invention;
FIG. 6 is a side elevation view of a load lock chamber of a heat-treating
apparatus of the present invention;
FIG. 7 is a plan view of a load lock chamber of a heat-treating apparatus
of the present invention, and which is provided with an interlock
mechanism for a maintenance door;
FIG. 8 is a frontal elevation view of a load lock chamber of a
heat-treating apparatus of the present invention, and which is provided
with an interlock mechanism for a maintenance door; and
FIG. 9 is a plan view of a door lock means used in the interlock mechanism
of the heat-treating apparatus of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following is a detailed description of preferred embodiments of the
present invention, with reference to the appended drawings.
In the present embodiment, the description will be given for the case when
the present invention is applied to a horizontal type of heat-treating
apparatus. As shown in FIG. 1, a load lock chamber 1 filled with a gas
other than oxygen, such as nitrogen (N.sub.2) or some other inert gas is
formed from stainless steel for example, into a rectangular prism shape
with length, width and height dimensions of 680 mm, 640 mm, 1520 mm
respectively, for example, and positioned towards the top of this load
lock chamber 1 is a horizontal type heat-treating apparatus 2. The inside
of this heat-treating apparatus 2 and the inside of the load lock chamber
1 are configured so as to be communicable via an upper end opening portion
of the load lock chamber 1.
The heat-treating apparatus 2 has an internal cylinder 4 that is formed
into a cylindrical shape from glass for example, and an outer cylinder 5
that is also formed of glass and is concentric with the internal cylinder
4. To the outer periphery of the outer cylinder 5 is provided a heater 2A
that heats the periphery of the outer cylinder 5. A manifold 6 comprised
of stainless steel for example, and which supports and fixes the internal
cylinder 4 and outer cylinder 5 is provided with a treating gas inlet pipe
7 that lead the processing as in, a treating gas exhaust pipe 8 that
exhausts the treating gas after treatment, and a vacuum exhaust system 9
that creates a vacuum inside the heat-treating apparatus 2. In addition, a
nitrogen supply source 52A and a hydrogen source 80A connected in parallel
to the treating gas inlet pipe 7 and via a switching valve 82A so as to be
freely switchable. Then, inside the internal cylinder 4 is housed a plural
number of semiconductor wafers 11 that are stacked and mounted at a
required pitch up and down a glass wafer boat 10. This wafer boat 10 is
provided via a temperature holding cylinder 13, to the cap portion 12 that
opens and closes and seals the lower end opening portion of the manifold
6. Then, the cap portion 12, temperature holding cylinder 13 and the wafer
boat 10 form one unit by the boat raising and lowering means 15 provided
inside the load lock chamber 1, and are configured so that the inside of
the load lock chamber 1 and the inside of the heat-treating apparatus 2
can be raised and lowered alternately.
On the other hand, to one of the side walls of the load lock chamber 1 is
provided a maintenance door 17 that is freely openable and closable by
workers performing periodic maintenance inside the load lock chamber 1.
This maintenance door 17 is securely fixed to the load lock chamber 1 by a
fixing means such as a bolt or the like when there is normal operation.
Then, the load lock chamber 1 is connected to a robot chamber 42 that is
air sealed via a gate valve 40. As shown in FIG. 2, inside this robot
chamber 42 is housed a cleaning apparatus (not shown) that removes a
natural oxidation film that has formed on a surface of semiconductor
wafers 11, and a moving apparatus 42A that moves semiconductor wafers 11
housed in a cassette 48A. As shown in FIG. 4 and FIG. 5, to the side wall
of this robot chamber 42 is formed a plural number of monitoring windows
73 of glass or the like to permit observation of the status of internal
operation.
Then, a cassette chamber 48 is airtightly connected to the robot chamber 42
via a gate valve 46 and as shown in FIG. 6, the configuration is such that
a cassette 48A that houses a plural number of semiconductor wafers can be
carried into and out of the cassette chamber 48 via the opening and
closing door 77.
Furthermore, as shown in FIG. 1, for example, nitrogen supply pipes 54, 56,
58 for the supply of nitrogen from a nitrogen supply source 52 are
respectively connected to the load lock chamber 1, the robot chamber 42
and the cassette chamber 48 via switching valve 60A, and 60B, 62, and 64
respectively. Also, the cleaning air supply system 80 is connected in
parallel with the nitrogen supply source via a switching valve 82, to
allow the supply of cleaning air to the nitrogen supply pipes 54, 56, 58
in accordance with necessity. In the same manner, to each of the chambers
1, 42, 48 are connected exhaust pipes 26, 66, 68 for the respective vacuum
exhausting of the chambers. Each of these exhaust pipes 26, 66, 68 are
connected to a vacuum exhaust system 70 provided with a turbomolecular
pump or the like, via an opening and closing valve (not shown) and a spare
port SP for sampling and a vacuum gauges VG for observation of the
pressure and the vacuum status.
In addition, as shown in FIG. 2 and FIG. 3, a ring-shaped flange portion
700 is formed at the lower distal end portion of the outer cylinder 5, and
a similar ring-shaped flange portion 800 is also formed at the upper
distal end portion of the manifold 6. Both of these ring-shaped flange
portion 700 and ring-shaped flange portion 800 are fixed by bolts 100 via
stopper members 900, and fix the outer cylinder 5 and the manifold 6.
In addition, to the contact surfaces of the ring-shaped flange portion 700
and ring-shaped flange portion 800 are provided O-rings 110 of fluorine
rubber or the like to maintain sealability. Also, between the upper
surface of the ring-shaped flange portion 700 and the stopper portion 900
is provided a flexible packing member 130 of carbon fiber for example,
which has good heat conductivity and promotes the discharge of heat from
the ring-shaped flange portion 700.
Furthermore, a ring-shaped protruding portion 140 is fixed to the inner
wall of the manifold 6 and this ring-shaped protruding portion 140
supports the lower distal end portion of the manifold 6. The upper portion
side wall of the manifold 6 is pierced by a treating gas inlet pipe 7 of
glass or the like, the distal end portion of which is upright and is
arranged between the outer cylinder 5 and the internal cylinder 4, and is
configured so that a spout portion 200 provided at the distal end portion
discharges treating gas between the two cylinders. Also, as shown in FIG.
2, to the treating gas inlet pipe 7 is connected an inert gas supply
source or a treating gas supply source such as a combustion apparatus 7A
that burns oxygen and hydrogen for the generation of steam when oxidation
treatment for example, is performed.
Furthermore, to the lower portion of the treating gas inlet pipe 7 is
formed a vacuum opening 9 that has a relatively large diameter of 60 mm
for example. Connected to this vacuum opening 9 via a vacuum exhaust pipe
valve 9B, is connected a vacuum exhaust system 9A provided with a
turbomolecular pump 9B for example, in a configuration where the interior
of the vessel can be made a vacuum to a degree of 10.sup.-6 Torr for
example. In addition, to the manifold 6 of a portion opposite the vacuum
opening 9 is formed an exhaust opening 260 for the exhaust of the treating
gas to outside the furnace. An exhaust pipe 8 is connected to this exhaust
opening 260, in a configuration where treating gas that has been used is
supplied to the treating gas exhaust system. Furthermore, to the upper
portion of the exhaust opening 260 is inserted a temperature measurement
fitting 8A for the measurement of the temperature inside the treating
chamber.
In addition, to the manifold 6 is provided a cooling means 300 for the
cooling of the entire manifold 6 when there is oxidation dispersion
treating. This cooling means 300 is configured to form a double pipe
structure that forms a cooling water path 310 that passes cool water
around the inside of the manifold 6.
Then, to the lower distal end portion of the manifold 6 is formed a
ring-shape flange portion 330. This ring-shape flange portion 330 is
configured by base bolts of stainless steel for example, and is supported
and fixed to the upper wall side of the load lock chamber 1 by bolts 360
and 370 and via an auxiliary member 350. Towards the bottom of the
manifold 6 is provided the load lock chamber 1 which requires airtightness
and so O-rings 410, 420 are provided between the auxiliary member 350 and
the upper surface of the ring-shaped flange portion 330, and to the
contact surface portions of the auxiliary member 350 and the base plate
340.
On the other hand, the cap portion 450 of stainless steel for example, at
the lower distal end opening portion of the manifold 6, is sealable via
O-ring 460. To this cap portion 450 is inserted a rotating shaft 470 that
can be freely rotated by a drive means (not shown). To the upper distal
end of this rotating shaft 470 is mounted a temperature holding cylinder
13 of glass for example. Then, as has already been described, to the top
of this temperature holding cylinder 13 is loaded the wafer boat 10 of
glass for example, and which is the processing boat. Inside this wafer
boat 10 are stacked for example, a plural number of semiconductor wafers
11 at a required pitch. Then, the cap portion 450 is configured so that
the temperature holding cylinder 13 and the wafer boat 10 can be raised
and lowered as a unit by the boat elevator 15.
Then, as shown in FIG. 1, the load lock chamber 1 is provided with an
interlock mechanism 20 for the maintenance door 17. More specifically,
this interlock mechanism 20 is configured by being provided with an oxygen
concentration detector 21 that detects the concentration of the oxygen
inside the load lock chamber 1, a door lock mechanism 22 provided in the
vicinity of the maintenance door 17 and for regulating the opening and
closing of the maintenance door 17, and a door lock control means 24 that
releases the lock of the door lock mechanism 22 when the oxygen
concentration detector 21 detects that the oxygen concentration is above a
required value.
The oxygen concentration detector 21 is provided to the exhaust pipe
connected to the exhaust opening at the lower portion side wall of the
load lock chamber 1. In particular, this oxygen concentration detector 21
is provided as close to the exhaust opening 25 as possible, and is
configured so that the oxygen concentration inside the load lock chamber 1
can be detected definitely. Moreover, the mounting position of the oxygen
concentration detector 21 can be at the bottom portion or the top portion
of the inside of the load lock chamber 1.
The output of this oxygen concentration detector 21 is connected to the
door lock control means 24, and when the detected oxygen concentration has
reached above of required value of 18% for example, the lock of the door
lock mechanism 22 is released and the maintenance door 17 can be opened.
As shown in FIG. 9, the door lock mechanism 22 is configured from a
cylinder 30 that is mounted to a required frame 22A, a piston 32 that is
moved out by the action of the compressed air or the like from inside the
cylinder 30, and a lock pin 36 at the distal end of the piston 32 and that
via a crank, rotatably moves in and out immediately before the load lock
chamber 1.
The mounting position of this door lock mechanism 22 is not limited to
immediately before the maintenance door 17, and as shown in FIG. 7, for
example, can be slightly separated from the maintenance door 17, at a
position where the opening operation of the maintenance door 17 is locked
at a degree of opening whereby a worker cannot place his head inside the
load lock chamber 1.
The following is a description of the operation of an embodiment of the
heat-treating apparatus of the present invention and having the
configuration described above.
First, when oxidation dispersion treatment is performed, the treating gas
exhaust pipe 8 connected to the manifold 6 of the heat-treating apparatus,
and the vacuum exhaust systems 25, 66, 68 connected to the robot chamber
42 and the cassette chamber 48, are driven for a long time and the entire
heat-treating apparatus is made in a vacuum status of 10.sup.-5 14
10.sup.-6 Torr for example. By this, the gases such as residual steam and
oxygen components that remain inside each of the chambers, 1, 42, 48 and
inside the treating vessel and which are the cause of the formation of a
natural oxidation layer are definitely removed from inside the apparatus.
After the completion of this exhaust operation, nitrogen gas is supplied
from the nitrogen supply source 52A and via the treating gas inlet pipe 7
to inside the treating vessel so that the pressure inside the treating
vessel becomes normal pressure. In addition, nitrogen gas is supplied from
the inert gas (nitrogen) supply source 52 so that the pressure inside the
load lock chamber 1, the robot chamber 42 and the cassette chamber 48
becomes normal pressure.
In this manner, once the internal pressure has become normal pressure, the
opening and closing door 77 opens and the cassette transport means (not
shown) transports the cassette 48A that houses a plural number (such as
25) of semiconductors, to inside the cassette chamber 48. The
semiconductor wafers inside this cassette chamber 48 are held by sheet
transfer means (not shown) and after the natural oxide film on the surface
of the wafers has been removed by cleaning, lowers inside the load lock
chamber 1 and the semiconductor wafers are successively housed inside the
wafer boat 10.
In this manner, once all of the semiconductor wafers 11 are housed inside
the wafer boat 10, the boat elevator 15 raises the wafer boat 10 and
houses it inside the heat-treating apparatus 2 as shown in FIG. 2. Then,
the cap portion 12 airtightly seals the lower distal end opening portion 3
of the manifold 6. All of these processes up till now have been performed
in an atmosphere of nitrogen at normal pressure and so there is no new
formation of natural oxide film to the semiconductor wafers 11. Also, one
each of these processes have finished, the each of the gate valves 40 and
46 are closed to stop movement of the gas in each of the chambers 1, 42,
48.
Then, when the semiconductor wafers 11 have been housed inside the
heat-treating apparatus 2, the heater 2A heats the heat-treating apparatus
2 to a required temperature of approximately 1200.degree. C. in the case
when oxidation dispersion processing is to be performed.
After this, the switching valve 82A is switched and hydrogen is supplied
from the hydrogen source 80A, and steam is generated by the combustion of
hydrogen and oxygen inside the combustion apparatus 7A, and this is
supplied from the discharge opening 200 via the treating gas inlet pipe 7,
to between the internal cylinder 4 and the outer cylinder 5, and the
pressure inside the treating vessel is maintained constant by exhausting
from the exhaust pipe 8 and the oxidation treating performed. At this
time, cooling water passes through the cooling water path 310 of the
cooling means provided to the manifold 6 and this metal manifold 6 is
cooled to a temperature of below 100.degree. C. or preferably to below
70.degree. C. thus metallic contamination of the semiconductor wafers and
corrosion of the surface of the manifold 6 is prevented. In particular, in
the case when the a corrosive gas such as POCl.sub.3 is used for the
oxidation dispersion processing, it is possible to control corrosion since
the manifold 6 is cooled to beneath the temperature described above.
Because of this, there is the prevention of the generation of particles
that become the cause of a lowered yield of semiconductor wafers 11. In
addition, at this time, if a cooling means comprising a water-cooled
jacket is also provided to the cap portion 450, the it is possible for an
enhanced corrosion suppression effect to be exhibited.
After oxidation dispersion processing has been performed for a required
time as has been described above, the supply of steam from the treating
gas inlet pipe 7 is stopped and then the vacuum exhaust system 9A is
driven again and the inside of the treating vessel is again made a vacuum
of 10.sup.-5 -10.sup.-6 Torr in the same manner as described above, and
after this, the gate valve 9B is closed and this status is held for a
required time so that it is possible to completely remove any steam
component and oxygen components that remain inside the treating vessel to
become the cause of the formation of a natural oxidation film.
Once the exclusion of the steam component and oxygen component has been
completed, an inert gas such as nitrogen is then supplied to inside the
processing vessel, and the internal pressure is made normal pressure.
Then, the boat elevator 15 lowers the wafer boat 10 and the semiconductor
wafers 11 that have been treated are transported from the treating vessel.
At this time, the load lock chamber 1 has a nitrogen atmosphere at normal
pressure. In addition, the inside of the treating vessel of the
heat-treating furnace and the load lock chamber 1 are communicated with
each other via the lower distal end opening portion of the manifold 6 but
as has been described, the residual steam component inside the treating
vessel has already been completely removed and so there is no flow of
steam components or the like to inside the load lock chamber 1.
After this, the reverse operation procedure is used to transport the
semiconductor wafers 11 that have been treated, to outside the apparatus
and via the robot chamber 42 and the cassette chamber 48. On the other
hand, untreated semiconductor wafers 11 are transported into the load lock
chamber 1 and an operation procedure the same as that described is
repeated.
In this manner, according to the present embodiment, there is a structure
whereby the inside of the heat-treating portion 2 can be made
substantially a complete vacuum, and whereby there is provided beneath it
a load lock chamber 1 that is filled with an inert gas such as nitrogen or
the like, and wherein before after the semiconductor wafers have been
treated, the residual steam component and oxygen component inside the
treating vessel are completely excluded to the exterior.
In addition, in the embodiment described above, it is necessary to create a
vacuum inside the heat-treating portion 2 and so it is necessary to
provide a metallic manifold 6 but his portion can have a cooling means 300
provided to cool the entire manifold 6 and so it is possible to prevent
the metallic contamination of the semiconductor wafers and the corrosion
of the manifold 6 when corrosive gases are used in oxidation dispersion
processing for example. Accordingly, it is possible to suppress the
generation of particles that cause a lowering of the yield of
semiconductor wafers 11 and to suppress the formation of natural oxidation
films.
Furthermore, the sealability is raised using a manifold for the creation of
a vacuum inside the treating vessel and so when compared to a conventional
glass oxidation dispersion vessel, it is possible to improve the
sealability with respect to toxic gases such as POCl.sub.3, and for the
safety of the workers to be enhanced.
In addition, in the embodiment described above, there is a double-walled
structure wherein the outer cylinder 5 and the internal cylinder 4 are
separated using the manifold and so when compared to a unitary
double-walled structure in a conventional oxidation dispersion apparatus,
it is possible to greatly reduce the manufacturing cost.
Moreover, in the embodiment described above, when the vacuum is created
inside the treating vessel, flowing high-temperature water to the cooling
means 300 of the manifold 6 in a configuration where the entire manifold 6
is heated by a heating means provided to the outer periphery of the
manifold 6 while the vacuum is being created enables the exclusion of
residual steam and the like from the treating vessel to be further
promoted and for there to be a reduction of the time required from exhaust
operation, and for the completeness of the exhaust operation to be
ensured.
In addition, the treating gas exhaust pipes for the vacuum exhaust pipes
and the treating gas do not have to be separately provided, as they can be
unified and the two functions switched by valve operation.
Furthermore, the embodiment described above can also be applied to normal
oxidation dispersion apparatus that do not have vacuums created inside
them, and can for example, be applied to CVD apparatus or other apparatus
which is not for oxidation dispersion processing.
As has been described above, according to the present invention it is
possible to definitely exclude the residual steam component and the oxygen
components from inside the heat-treating portion and for the flow of a
steam component or the like to the inside to be prevented and so, it is
possible to suppress the formation of a natural oxidation film to the
surface of the semiconductor wafers.
Accordingly, it is possible to accurately form a uniform oxidation film of
good quality of a semiconductor wafer surface to be treated, and for the
demands for high integration of semiconductor products such as
semiconductor wafers to be met.
The following is a description of operation for the case for periodic
maintenance of the load lock chamber 1.
For example, it is necessary to open the maintenance door 17 of the load
lock chamber 1 in order to clean and remove a film that has formed on a
glass fitting such as a wafer board 10 when heat treating has been
performed for the required number of times, or to allow maintenance and
inspection of the boat raising and lowering means 15 inside or the load
lock chamber 1. However, the load lock chamber 1 and the reaction vessel
are in the status where they are filled with nitrogen at normal pressure.
Moreover, at this time, the gate valve 40 is closed and partitions off the
side of the robot chamber 42.
First, as shown in FIG. 7, the description will be for the case where is
installed at the position indicated by the broken line, where it is
slightly separated from the door lock mechanism 22.
When there is inspection and maintenance of the internal mechanism inside
the boat raising and lowering means 15 of the load lock chamber 1, the
wafer boat 10 is housed inside the treating vessel and the opening portion
3 of the manifold 6 is sealed airtight by the cap portion 12. On the other
hand, cleaning the wafer boat 10 involves lowering the wafer boat 10 to
inside the load lock chamber 1 beforehand, and taking it from the load
lock chamber 1 to outside.
When this is done, the oxygen concentration inside the load lock chamber 1
is detected by the oxygen concentration detector 21 and that detection
value is transmitted to the door lock control means 24. Then, the door
lock control means 24 controls the locking and unlocking of the door lock
mechanism 22 in accordance with the value of the detected oxygen
concentration.
Even if the worker who is performing maintenance removes the bolts and the
like that fix the maintenance door 17 and attempts to completely open the
maintenance door 17 when the nitrogen concentration inside the load lock
chamber 1 is still high and the value of the oxygen concentration is less
than 18%, the maintenance door 17 will contact the lock pin 36 even if it
is opened partially and will not open further. At this time, the opening
distance of the maintenance door 17 is a set at a distance of 10-15 cm for
example, which is such that the maintenance person cannot put his head
inside. Because of this, if the oxygen concentration is still low, then it
is not possible for a maintenance person enter beforehand to speed up the
maintenance process, and therefore it is possible to prevent asphyxiation
accidents.
In this manner, in the status where the maintenance door 17 is partially
opened, the nitrogen inside the load lock chamber 1 is naturally replaced
with the clean air inside the clean room outside, and the oxygen
concentration inside rises gradually. Then, when replacement has proceeded
and the oxygen concentration detector 21 detects that the oxygen
concentration inside the load lock chamber 1 has reached 18%, the door
lock control means 24 operates the cylinder 30 and the lock pin 36 of the
door lock mechanism 22 is rotated to retreat and release the lock of the
maintenance door 17. As a result, as shown in FIG. 7, it is possible for a
maintenance person to fully open the maintenance door 17, and to perform
maintenance work inside the load lock chamber 1 in a safe atmosphere.
In particular, when there is the natural replacement of the nitrogen inside
the load lock chamber 1, there is always downflow of clean air inside the
clean room wherein the heat-treating apparatus is installed and so the
nitrogen inside the load lock chamber 1 is gradually replaced from the
top.
The following is a description for the case where, as shown in FIG. 7, the
door lock mechanism 22 is provided at a position indicated by the solid
line, and is substantially in contact with the maintenance door 17.
In this case, it is not possible to have the natural replacement of the
nitrogen inside the load lock chamber 1 as described above, since the
maintenance door 17 can only open slightly, and so forced air replacement
is performed for the load lock chamber 1.
In this case, as described with reference to FIG. 1, the vacuum exhaust
system 70 connected to the load lock chamber 1 first exhausts the nitrogen
inside the load lock chamber 1 to outside via the exhaust opening 25 and
creates a vacuum inside the load lock chamber 1. Then, this vacuum exhaust
system 70 either is stopped, or is driven to introduce clean air from the
clean air supply source 80 to into the load lock chamber 1 via the supply
pipe 54. In this process, if the oxygen concentration detector 21 detects
that the oxygen concentration has reached 18% for example, then as
described above, the lock pin 36 of the door lock mechanism 22 is rotated
by the cylinder 30 and retreats from the front surface of the maintenance
door 17 and unlocks the door. As a result, the worker can fully open the
maintenance door 17 and perform maintenance work inside the load lock
chamber 1 in a safe atmosphere.
Moreover, even if clean air is supplied and the pressure inside the load
lock chamber 1 is normal pressure, but the oxygen concentration still has
not reached a required value, there is insufficient vacuum exhaust
operation to exclude the nitrogen and so further vacuum operation of the
inside is performed. Here, when there is forced replacement, the reason
for using clean air is that compressor oil and other contaminants are
contained in the air that is used in factories and this oil would result
in contamination of the inside of the apparatus. In addition, in the
embodiment described above, the set oxygen concentration is not limited at
18%, but can be set around 10% for example, but in any case is made a
concentration where a worker would not asphyxiate.
Moreover, in the embodiments described above, the description was given for
the case where the present invention is applied to a heat-treating
apparatus such as a CVD apparatus or an oxidation dispersal apparatus or
the like, but the present invention is not limited to this, as it can of
course be applied to load lock chambers that handled gases other than
oxygen.
In the above, according to the present invention, air other than oxygen
inside a load lock chamber is replaced, and until the oxygen concentration
attains a required value, it is possible to lock a maintenance door so
that it cannot open fully. Accordingly, the early entry of a maintenance
person into the load lock chamber is strictly prevented while the oxygen
concentration is low and so it is possible to enhance the safety of
maintenance persons inside.
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